1. Field of the Invention
This invention relates to a water-proof device for an electrocardiograph transmitter used for recording an electrocardiogram in order to learn the condition of the heart of a man exercising underwater, such as swimming or underwater rehabilitation.
2. Prior Art
As a result of the recent development of the medical technology and improvement of the general diagnosis and treatment levels concerning the heart, many heavy and light heart disease patients have been found, thus contributing to the therapy of heart diseases.
However, light heart disease patients and also school children suffering from heart diseases found in nation-wide heart conducted in schools are inhibited from receiving lessons in swimming which is a hard physical exercise.
In the infant's cardiology so far, the basis, on which a decision that a school child suffering from a light heart disease can safely exercise swimming is made, is constituted by the results of study of an electrocardiogram of the child on the ground and not while swimming.
However, the status of the circulatory system of a man during swimming is peculiarly different from the motion on the ground, and the status of the circulatory system of a school child during swimming has not been accurately analyzed. Therefore, the safety of a school child suffering from a heart disease during swimming cannot be confirmed. Therefore, it has been difficult to allow the swimming of a child suffering from a light heart disease, who is thought as a result of the conventional heart examination that he or she can safety exercise swimming.
For the above reason, it has become an urgent necessity to verify that the swimming of the child as noted above is safe in view of his or her electrocardiograph during swimming.
In order to record an electrocardiogram of a man during swimming, it is necessary to attach electrodes to the skin, connect these electrodes to an electrocardiograph installed on the ground through a cable, let the man with the electrodes swim and detect a minute current from the heart as induced on the skin during the swimming with the electrocardiograph installed on the ground through the cable, thus measuring a change in the potential generated in the man with the electrocardiograph.
When recording the electrocardiograph of the man during swimming with the electrocardiograph installed on the ground, a long cable is required if the man is to cover a long distance by swimming. Increasing the cable length, however, leads to increased expenditures for the recording. In addition, when the cable length is increased, the minute signal derived from the heart is liable to be lost before it reaches the electrocardiograph through the cable. In such a case, an accurate electrocardiogram cannot be obtained. Further, when the swimming is done violently, it is liable that the cable entangles on the hands and legs, making the swimming difficult.
To overcome this difficulty, it has been proposed to record by radio an electrocardiographic signal of a man moving in water under remote control.
This method will now be described with reference to FIGS. 3 and 4. Referring to FIG. 3, water-proof electrodes 1 to 3 are attached to the skin of a man. These water-proof electrodes 1 to 3 are connected by leads 4 to 6 to a transmitter 7 which generates a radio signal.
The transmitter 7, to which the water-proof electrodes 1 to 3 are connected through the leads 4 to 6, is installed by a mounting belt 8 on the skin of the swimmer, as shown in FIG. 4. While the swimmer is swimming with the transmitter 7, an electrocardiographic signal is detected by the water-proof electrodes 1 to 3 and supplied through the leads 4 to 6 to the transmitter 7.
The electrocardiographic signal led to the transmitter 7 is transmitted from an antenna 9. The transmitted electrocardiographic signal is intercepted by an antenna 11 of a receiver 10 which is installed on the ground. The received electrocardiographic signal is displayed on a cathode-ray tube 12 or recorded on a recording sheet 13 as an electrocardiograph.
When this method is adopted, since no cable is used, it is possible to eliminate leakage of current. Also, motion in water is never interrupted. However, water is liable to be introduced into the transmitter 7, and in such a case an accurate electrocardiograph cannot be obtained.